Above is a picture distinguishing mold from another type of fungus, yeast, and it provides insight into some of the classification characteristics of bread mold in general.
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Classification/Diagnostic Characteristics
Bread Mold:
Domain: Eukarya
Kingdom: Fungi
Phylum: Zygomycota
Class: Zygomycetes
Order: Mucorales
Family: Mucoraceae
Genus: Rhizopus
Species: Rhizopus Stolonifer
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Rhizopus Stolonifer is often called black bread mold because of the black spores that it leaves on bread that are visible to the eye. (2) Bread mold is a part of the Zygomycota group of fungi, or Zygospore fungi, and is also fuzzy in appearance. Its reproductive structure consists of a unicellular zygospore with many diploid nuclei in a zygosporangium. Black bread mold appears to be like a fluffy, gray mass or a blue or yellow colored coating on the substrate. (2)
Bread mold can be found in the common household and most often looks like the substance on the slices of bread above.
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This is a picture that examines bread mold from under a microscope.
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Relationship to Humans
Bread mold can be found on different types of bread and can be used in certain types of food production. If it is consumed, it can cause infections in humans. Rhisopus Stolonifer is used in medications such as birth control pills, as it produces the steroids within its cells that are commonly used. (2)
Habitat and Niche
Fungi, such as bread mold, typically live in liquid or moist environments and can quickly spread within a few days in such an environment. An example of a moist environment would be ripe fruit. Rhizopus stolonifer perfers warm as well as dry habitats, such as wild bird nests, fresh decaying litter, and soils. (2)
Predator Avoidance
The main defense mechanism that bread mold uses to avoid predators is through the release of mycotoxins, which are naturally produced substances that can be toxic to other life forms. (9) Another subtle defense mechanism can occur when bread mold encounters the mold mite, which tends to develop in moist, humid areas. Even though bread mold does not employ a particular defense mechanism in this case, it can avoid the predator by growing in dry conditions that are not suitable for the mold mite to flourish. It can survive in this particular environment through the production of zygosporangium. (4)
Nutrient Acquisition
Fungi undergo a process known as absorptive heterotrophy, a successful mode of nutrition acquisition in a variety of environments, in which they obtain their food by secreting digestive enzymes into the environment to break down large food molecules into soluble breakdown products that they then absorb. (13) The mold spreads over the surface of the food particle, sending it's hyphae inward to absorb the nutrients, particularly sugar and starch, which it stores as glycogen. (5) This process occurs through extracellular digestion by means of enzymatic hydrolysis in which the addition of water breaks the bonds between the sugars. The particles are absorbed by rootlike structures called rhizoids. (10)
Reproduction and Life Cycle
Bread mold is a haplontic organism, meaning that the main form of the organism in the life cycle is haploid and the diploid zygote is formed only briefly. It goes through the following steps for sexual reproduction and the life cycle:
The zygote, which is the only diploid cell in the life cycle, immediately undergoes meiosis after it is formed and produces more haploid cells.
These haploid cells, which are normally spores, are what comprise the dispersal units for the bread mold.
The spores grow to form a new haploid organism that can be either single-celled or multicellular.
The cells of the haploid organism then produce gametes that will fuse together and form the diploid zygote.
Therefore, in the reproduction cycle, the mature organism is haploid and the zygote is diploid. (15) Zygospore fungi, such as bread mold, sexually reproduce when the adjacent hyphae of two different mating types (no morphological distinction between male and female but rather genetically determined distinction exists between different mating types) release pheromones, which cause them to grow toward each other. The hyphae then produce gametangia, in which the nuclei replicate without cell division. Then, the two gametangia fuse to form zygosporangium with many haploid nuclei from each mating type. Next, the pairs of haploid nuclei form multiple diploid nuclei within a unicellular zygospore. Rhizopus produce many stalked sporangiophores that each bear a single sporangium with hundreds of minute spores, which is a form of asexual reproduction. (13)
The picture above depicts the typical life cycle of organisms classified under the rhizopus genus. It shows steps beginning with the growth of hyphae towards each toward, then the fertilization that occurs, the development of the zygosporangium and sporangium, and finally the formation of spores.
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This picture shows a more detailed diagram of the asexual and sexual reproduction that bread mold undergoes.
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Growth and Development
After the zygospore is formed, it is protected by a thick, multilayered cell wall and then remains in a resting stage for up to months before the nuclei undergo meiosis and a stalked sporangiophore sprouts, bearing one or many sporangia. Each one contains haploid nuclei that are incorporated into spores, which disperse and develop to form new haploid hyphae. The total hyphal growth of fungal mycelium can exceed one kilometer per day. (13)
This picture indicates how bread mold also undergoes asexual reproduction during the formation of spores.
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In addition, this picture shows how the structure shown above would form in bread.
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Integument
The body of the multicellular fungus is called a mycelium, which is composed of individual tubular filaments called hyphae, where nutrient absorption takes place. The cell walls of the hyphae are strengthened by the microscopic fibrils of chitin. (13)
Movement
Bread mold does not possess a flagellum and therefore is immobile. Spores can travel in the air to find a habitable location, and the spores are actually very "commonly found in air" (3). They are also spread when they land on vegetation that is consumed by a herbivore, which then discharges them through the removal of its feces. (8) In addition, the growth of the hyphae allows for the bread mold to spread out further.
Sensing the Environment
By producing zygosporangium, bread mold is capable of surviving in a harsh natural environment, meaning one that is not warm/moist. (13) Also, when adjacent hyphae of two different mating types release pheromones, they will grow toward each other and sexual reproduction will take place. The filamentous hyphae are beneficial for bread mold as well to help it sense its physical environment and remain close to its source of nutrition. (13)
Gas Exchange
Fungi are decomposers that feed on dead organic matter, which includes bread. They digest the organic matter and then break it down into simpler chemicals. Other substances such as carbon, nitrogen, and minerals, are then returned to the atmosphere. (7) The gas exchange in bread mold occurs across the hyphae that comprise the mycelium. (12)
Waste Removal
Most wastes are water soluble and therefore diffuse from the hyphae into the environment. (12)
Environmental Physiology
(temperature, water, and salt regulation)
Fungi are in intimate contact with their environment. The large surface area-to-volume ratio for fungal mycelium is beneficial for absorptive heterotrophy because all of the hyphae are close to the food source. However it is also detrimental because fungi then tend to lose water rapidly in a dry environment, which is why they are most commonly found in moist environments. Many fungi grow in temperatures as low as -6 degrees Celsius and some can tolerate temperatures above 50 degrees Celsius, which shows that fungi tolerate temperature extremes. For example, mold can be found in the refrigerator or on fruits lying on the counter. Fungi are also often tolerant of hypertonic environments. Bread mold can survive in a harsh natural environment, meaning one that is not warm/moist, by producing zygosporangium. (13)
Internal Circulation
In multicellular fungi, pores in the septa, the incomplete cross-walls that subdivide the hyphae, allow for the movement of organelles and other materials between compartments in separate mycelia. (13)
Chemical Control
Zygospore fungi sexually reproduce when the adjacent hyphae of two different mating types release chemical signals called pheromones. (13) Therefore, bread mold does possess an endocrine system that allows for the release of such chemical signals.
Review Questions:
1. How does bread mold use sexual reproduction to replicate? How does asexual reproduction also play a role in the life cycle of bread mold?
2. Why/when is the mycelium and hyphae of fungi both beneficial and detrimental? 3. What potential does fungus have in biotechnology? 4. Explain how bread mold undergoes absorptive heterotrophy and its purpose.
13. Hillis, David M., David Sadava, Craig Heller, and Mary V. Price. "The Evolution and Diversity of Fungi." Principles of Life. Sunderland, MA: Sinauer Associates, 2012. 437-55. Print.
15. Hillis, David M., David Sadava, Craig Heller, and Mary V. Price. "Different Life Cycles Use Different Modes of Reproduction." Principles of Life. Sunderland, MA: Sinauer Associates, 2012. 126-27. Print.
Table of Contents
http://snowtaxonomy2013.wikispaces.com/Yeast+%28fungus%29
(1)
Classification/Diagnostic Characteristics
Bread Mold:
- Domain: Eukarya
- Kingdom: Fungi
- Phylum: Zygomycota
- Class: Zygomycetes
- Order: Mucorales
- Family: Mucoraceae
- Genus: Rhizopus
- Species: Rhizopus Stolonifer
(3)Rhizopus Stolonifer is often called black bread mold because of the black spores that it leaves on bread that are visible to the eye. (2) Bread mold is a part of the Zygomycota group of fungi, or Zygospore fungi, and is also fuzzy in appearance. Its reproductive structure consists of a unicellular zygospore with many diploid nuclei in a zygosporangium. Black bread mold appears to be like a fluffy, gray mass or a blue or yellow colored coating on the substrate. (2)
(17)
(14)
Relationship to Humans
Bread mold can be found on different types of bread and can be used in certain types of food production. If it is consumed, it can cause infections in humans. Rhisopus Stolonifer is used in medications such as birth control pills, as it produces the steroids within its cells that are commonly used. (2)
Habitat and Niche
Fungi, such as bread mold, typically live in liquid or moist environments and can quickly spread within a few days in such an environment. An example of a moist environment would be ripe fruit. Rhizopus stolonifer perfers warm as well as dry habitats, such as wild bird nests, fresh decaying litter, and soils. (2)
Predator Avoidance
The main defense mechanism that bread mold uses to avoid predators is through the release of mycotoxins, which are naturally produced substances that can be toxic to other life forms. (9) Another subtle defense mechanism can occur when bread mold encounters the mold mite, which tends to develop in moist, humid areas. Even though bread mold does not employ a particular defense mechanism in this case, it can avoid the predator by growing in dry conditions that are not suitable for the mold mite to flourish. It can survive in this particular environment through the production of zygosporangium. (4)
Nutrient Acquisition
Fungi undergo a process known as absorptive heterotrophy, a successful mode of nutrition acquisition in a variety of environments, in which they obtain their food by secreting digestive enzymes into the environment to break down large food molecules into soluble breakdown products that they then absorb. (13) The mold spreads over the surface of the food particle, sending it's hyphae inward to absorb the nutrients, particularly sugar and starch, which it stores as glycogen. (5) This process occurs through extracellular digestion by means of enzymatic hydrolysis in which the addition of water breaks the bonds between the sugars. The particles are absorbed by rootlike structures called rhizoids. (10)
Reproduction and Life Cycle
Bread mold is a haplontic organism, meaning that the main form of the organism in the life cycle is haploid and the diploid zygote is formed only briefly. It goes through the following steps for sexual reproduction and the life cycle:
- The zygote, which is the only diploid cell in the life cycle, immediately undergoes meiosis after it is formed and produces more haploid cells.
- These haploid cells, which are normally spores, are what comprise the dispersal units for the bread mold.
- The spores grow to form a new haploid organism that can be either single-celled or multicellular.
- The cells of the haploid organism then produce gametes that will fuse together and form the diploid zygote.
Therefore, in the reproduction cycle, the mature organism is haploid and the zygote is diploid. (15)Zygospore fungi, such as bread mold, sexually reproduce when the adjacent hyphae of two different mating types (no morphological distinction between male and female but rather genetically determined distinction exists between different mating types) release pheromones, which cause them to grow toward each other. The hyphae then produce gametangia, in which the nuclei replicate without cell division. Then, the two gametangia fuse to form zygosporangium with many haploid nuclei from each mating type. Next, the pairs of haploid nuclei form multiple diploid nuclei within a unicellular zygospore. Rhizopus produce many stalked sporangiophores that each bear a single sporangium with hundreds of minute spores, which is a form of asexual reproduction. (13)
(6)
(16)
Growth and Development
After the zygospore is formed, it is protected by a thick, multilayered cell wall and then remains in a resting stage for up to months before the nuclei undergo meiosis and a stalked sporangiophore sprouts, bearing one or many sporangia. Each one contains haploid nuclei that are incorporated into spores, which disperse and develop to form new haploid hyphae. The total hyphal growth of fungal mycelium can exceed one kilometer per day. (13)
(11)
(16)
Integument
The body of the multicellular fungus is called a mycelium, which is composed of individual tubular filaments called hyphae, where nutrient absorption takes place. The cell walls of the hyphae are strengthened by the microscopic fibrils of chitin. (13)
Movement
Bread mold does not possess a flagellum and therefore is immobile. Spores can travel in the air to find a habitable location, and the spores are actually very "commonly found in air" (3). They are also spread when they land on vegetation that is consumed by a herbivore, which then discharges them through the removal of its feces. (8) In addition, the growth of the hyphae allows for the bread mold to spread out further.
Sensing the Environment
By producing zygosporangium, bread mold is capable of surviving in a harsh natural environment, meaning one that is not warm/moist. (13) Also, when adjacent hyphae of two different mating types release pheromones, they will grow toward each other and sexual reproduction will take place. The filamentous hyphae are beneficial for bread mold as well to help it sense its physical environment and remain close to its source of nutrition. (13)
Gas Exchange
Fungi are decomposers that feed on dead organic matter, which includes bread. They digest the organic matter and then break it down into simpler chemicals. Other substances such as carbon, nitrogen, and minerals, are then returned to the atmosphere. (7) The gas exchange in bread mold occurs across the hyphae that comprise the mycelium. (12)
Waste Removal
Most wastes are water soluble and therefore diffuse from the hyphae into the environment. (12)
Environmental Physiology
(temperature, water, and salt regulation)Fungi are in intimate contact with their environment. The large surface area-to-volume ratio for fungal mycelium is beneficial for absorptive heterotrophy because all of the hyphae are close to the food source. However it is also detrimental because fungi then tend to lose water rapidly in a dry environment, which is why they are most commonly found in moist environments. Many fungi grow in temperatures as low as -6 degrees Celsius and some can tolerate temperatures above 50 degrees Celsius, which shows that fungi tolerate temperature extremes. For example, mold can be found in the refrigerator or on fruits lying on the counter. Fungi are also often tolerant of hypertonic environments. Bread mold can survive in a harsh natural environment, meaning one that is not warm/moist, by producing zygosporangium. (13)
Internal Circulation
In multicellular fungi, pores in the septa, the incomplete cross-walls that subdivide the hyphae, allow for the movement of organelles and other materials between compartments in separate mycelia. (13)
Chemical Control
Zygospore fungi sexually reproduce when the adjacent hyphae of two different mating types release chemical signals called pheromones. (13) Therefore, bread mold does possess an endocrine system that allows for the release of such chemical signals.
Review Questions:
1. How does bread mold use sexual reproduction to replicate? How does asexual reproduction also play a role in the life cycle of bread mold?
2. Why/when is the mycelium and hyphae of fungi both beneficial and detrimental?
3. What potential does fungus have in biotechnology?
4. Explain how bread mold undergoes absorptive heterotrophy and its purpose.
Picture:
1. http://www.healthcentral.com/common/images/1/19348_9942_5.jpg
2. http://bioweb.uwlax.edu/bio203/2011/olbrantz_chri/interactions.htm
3. http://tolweb.org/treehouses/?treehouse_id=4817
4. http://www.mouldportal.com/mould_mites.html
5. http://bioweb.uwlax.edu/bio203/2011/olbrantz_chri/nutrition.htm
6. http://bio.rutgers.edu/~gb101/lab6_protists/rhizolife.jpg
7. http://www.nmnaturalhistory.org/assets/files/Education/Cirricula/Fungi_Chapter.pdf
8. https://www.boundless.com/biology/fungi/fungi-a-diverse-group/zygomycetes/
9. http://www.knowmycotoxins.com
10. http://www.biog1445.org/demo/05/fungi.2a.html
11. http://www.backyardnature.net/f/rhizopus.gif
12. http://answers.yahoo.com/question/index?qid=20081219095701AA6ICvb
13. Hillis, David M., David Sadava, Craig Heller, and Mary V. Price. "The Evolution and Diversity of Fungi."
Principles of Life. Sunderland, MA: Sinauer Associates, 2012. 437-55. Print.
14. http://worldundermicroscope.files.wordpress.com/2013/01/img00026.jpg
15. Hillis, David M., David Sadava, Craig Heller, and Mary V. Price. "Different Life Cycles Use Different Modes of
Reproduction." Principles of Life. Sunderland, MA: Sinauer Associates, 2012. 126-27. Print.
16. http://www.fitsana.com/black-bread-mold-facts/
17. http://www.fitsana.com/how-does-mold-grow-on-bread/